Viral diseases continue to be a major threat to both the pediatric as well as the adult patient population. In recent years, the rapid emergence and spread of relatively new human pathogens such as HIV and SARS, the increasing morbidity and mortality associated with persistent and prolonged infection with agents such as Hepatitis C as well as the episodic and often unexplained reemergence of pathogens underscores the necessity of having well trained investigators that can respond rapidly to these public health demands. The goal of this research training grant is to prepare physicians (MD and MD/PhDs) to pursue careers as independent investigators specifically in the area of viral pathogenesis with a primary focus on virus/host interactions. Each of the twelve faculty members representing the key training personnel for this program has a strong track record in the area of viral pathogenesis as reflected in both publications as well as funding and a commitment to training physician-scientists. Each plays a major role in the graduate school as well as their respective departments and has developed extensive collaborative interactions which will provide the trainee a critical and accessible network of expertise. The institutional commitment in this area is reflected by the recent creation of the Emerging Infections Center that will allow continued recruitment of outstanding faculty to reflect Mt. Sinai and will provide an additional framework for trainees to benefit from the interdisciplinary nature of research in this arena. The training program is designed to extend the training period of physicians following completion of their clinical fellowships, particularly in Adult and Pediatric Infectious Diseases. The candidates will enter into their research training track in their second year of fellowship and will be candidates for funding through the training grant for two subsequent years. The major activity (representing 90% of their time) during these two years will be mentored laboratory investigation on an individual project. This experience will be complemented by participation in a weekly journal club, weekly laboratory data sessions as well as divisional, departmental, and institutional research conferences. The goal of this program is to provide the candidate with the necessary skills and training to effectively compete for mentored scientist awards as the next step in their transition to independent careers as physician scientists.